Screw cap molding machine



April 27, 1943. w. sTRAuss SCREW CAP MOLDING MACHINE 4 sheets-sheet 1Filed Dec. 22, 1938 INVENTOR.

WILL/HM STR/,USS BY llnllllllllllllllllilllllnlll .IIIIII A TToRNEY lApril 21, 1943. NTRA-USS v2,317,823

--scREw CAP MoLDINc;v MACHINE Filed Dec. 22. 1958-1 4 Smets-sheet 2INVENTOR.v

Y www A TTORNEY v//LL/AM STR/wss April 27,1943. n w. smAuss 2,?1723-SCREW CAP MOLDING MAQHINE Filed Dec. 22, 1958 44 Sheets-Sheet 5 lNVENTOR. WILL/AM STRAUSS BYWSASW A TTORNEY Patented Apr. 27, 1943 SCREWCAP MOLDING MACHINE William Strauss, Philadelphia, Pa., assignor to F.J. Stokes Machine of Pennsylvania Company, a corporation ApplicationDecember 22, 1938, Serial No. 247,215 In Great Britain August 11, 1938 6Claims.

. This invention relates to plastic-'molding machines and, moreparticularly,` to an automatic machine for the molding of ilnishedarticles from pulverulent compounds such as, for' example,

Bakelite molding Acompound,4 a phenolic condensation product whichhardens into the shape of the mold through the application of heat andpressure.

One purpose of this invention is to provide modifications andimprovements of thei Automatic molding machine described in theapplication of Victor I. Zelov and William Strauss, Serial #146,550, sothat parts embodying screw threads such as bottle and jar caps, may besuccessfully molded in such a machine.

' It is one object of the present invention to provide an apparatus forautomatically manufacturing parts having molded screw threads frommolding materials suoli as the kind referred to, which will be simple incontruction and so arranged that each step of the molding cycle may beautomatically timed by means of a repeating controller whereby theerrors inherent to manual control are eliminated.

It is also a purpose of my invention to provide' unitary machine whichis entirely` automatic throughout the molding cycle and suitable for theeconomical manufacture of threaded parts from molding compounds in thecommon type of mold usually referred to as positive, semi-positive orflash type of mold.

The invention includes such novel features as a rotatable die or dieholder;

A motor for rotating the die;

A switch controlling the supply of current to the motor; A

Means for controlling the operation of the (Figs. 1, 2, and -3) a moldsuitable for the production of screw caps from plastic material such asphenolics, ureas, cellulose acetate, methyl methacrylate, etc., of whichthere now is available a large variety, the mold I8 when open as shownin Fig. 2, being supplied by the feed kdevice il, with a suflicientquantity of any one of these materials and then allowed to close asshown in Fig. 3, where the required pressure and heat is applied asuflicient length of time to effect the molding and curing,l thusproducing a piece as shown for example in Figs. 6 and 7.

The mold is of a conventional type and comprises a die 3|, provided witha suitable cavity 38, mounted in a holder 32,'resting on the lowerplaten 35 and a punch 28, attached to the upper platen-26. The upperplaten 26 is provided with heatlngmeans 21 and a temperature control 25switch and other features that will be apparent Y' from the drawings andspecifications.

Referring to the drawings:

Fig. 1 is a front elevation partly in section. showing so much of amachine suitable for my purpose asis necessary to embody theimprovements.

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a sectional view through the die andV switch mechanism.

Fig, 4 is a front elevation of the controller. Fig. 5 is a iragmentarysection taken on line 5^5 of Fig. 4.

Figs. 6 and 7 show respectively a top view of a'molded cap and a sectionthrough it.

in the drawings there is shown a machine similar to one shown anddescribed in the application of -Victor I. Zelov and William Strauss,Serial #146,550, filed June 5, 1937. Thismachire was selected and usedonly for the purpose of showing the principles of application and modeof operation of my invention. There ls shown at il) low and imperfectthreads.

and is mounted on the ram l I. The lower platen 35 is provided withheating means 34 and temperaturevcontrol 36 and is attached to crosshead44 v.of the pressure frame I3, Die holder 32 has a stem or spindle 38extending down through lower platen 35 andconnected to shaft 48 of motorI8 by the coupling 39.

On punch 28 may be seen grooves 2lia cut or formed in the cylindricalsurface which will produce on the molded piece corresponding raisedconfigurations. This may t'ake the path of a helix thus forming a screwthread or combine a helix with a complete groove so as to form a raisedring 29 at the end of punch 28 and thereby produce both a screw thread-46 (Fig. '1) and an undercut 41. It is, of course, understood that thegroove4 for threads or undercut, as the case may be, may also be cut inthe diecavity 3c, instead of onk punch 28 in which case however, thethread would appear on the 'outside of the molded. piece.

In conventional molding of screw caps itis customary to eject the moldedpiece either by stripping it oil the punch in an axial direction orunscrew it after thc mold is fully opened. Thr` stripping of a cap likethe one shown in Fig. 7

with its screw thread 45, 46 and undercut or garket recess 41 is notvery satisfactory as this method only permits the molding of rathershal- 'Ithreads of the standard configuration vcould not be stripped.Unscrewing istherefore preferable in all cases and necessary whereperfectly molded threads are desired. When pieces with `screw threads onthe outside surface are molded, it would of course. be'impossible to usethe stripping method. In conventional molding very complicated mechansmshave been resorted to in the past for unserewing but they are slow andcumbersome, and

are usually manually operated. Through my invention, unscrewing of thethreaded piece as it is being ejected from the Vmold is mechanicallyvthe means for operating the molding Il, supporting a ram I I with itsoperating mechanism connected to the reversing motor Il, which beprovided at any convenient place, for example,

l in the aperture provided for spindle ll as it is controlled through.the reversing switch 24 from controller 20 so as to close or open themold. On the frame Il is also mounted a pressure frame I3 with itscrosshead M and provisions 42 in` the form of'a spring for producing thepressure required to be exerted on the molding compound while curing.Withinframe I2 is mounted an- Y other frame I2, rigidly connected to theram II, and therefore only acting and moving in conjunction with ram II.This frame I2 provides powderV measuring and feeding device I'l in timedrelation' with the movement of the ram II. for master controller 20enters through switch 22 and furnishes the energy required for operatingthe motor 49 which drives the controller chains 5B, carrying the controlbars 5I, which actuate the various dogs 52 to open and close circuits intimed relation or synchronism, causing the machine to functionautomatically. Just as the pressure on mold I0 should vary according tothe kind of molding compound and size of piece molded and therefore ismade adjustable by increasing or decreasing the pressure 'exerted bysprings 42, so the desired curing time varies and can be set to suit therequirements bymeans of timer 23, which is so connected in the circuitthat lwhen once set for the required curing time, the master controllerwill start it and, after starting the timer, will stop until againrestarted by timer 23, for the purposeof putting the machine through itspaces of opening the mold, ejecting and discharging the molded piece,cleaning the mold, measuring andv feeding the measured charge to themold cavity, closing the mold, cleaning the face ofthe die around thepunch and holding the mold closed under pressure the required length oftime. With many pieces an additional step', that of breathing ordegasing, must be introduced at acertain timein'the curing period andthis is taken care of by the proper setting of a set of dogs on thecontroller 20, so that the mold after a suitable time, will be openedfor the required length of' breathing `time and then closed again forthe curing period. 'I'he extreme limit for the movement of the ram II,is

controlled by a pair of limit switches 2l, one of whichacts to stop themotor when-the ram has reached its topmost point of travel, and theother'acts to stop the motor on its downward stroke when theproperpressure. is applied to the pressed so as to dwell underthe-required tension from springs 42. An operating check Il is used forthe purpose of controlling the continuity of charged. but in case offailure to discharge a molded piece, the operation check functions tostop the machine before any damage can be done.

The current passes through the lower platen To hold the die holder 32from up or down movement, a collar 21 may be fastened to spindle I8. Anykind of a die II, with a suitable cavity may be mounted within dieholder 32, so as to .act in conjunction l with a proper punch 28 inmolding articles from plastic material. The customary heatsupplyingmeans are provided at-2I for upper platen 26 and at 3l for the lowerplaten Il and temperature control means are indicated at 25 for theupper vplaten 28 and at 3l for lower platen 35. The

source of heat which may be electric, steam or gas, ofcourse vdeterminesthe type of control needed. 'I'he moldingy of a piece from plasticmaterial will proceedin the conventional way until the point of ejectingand discharging the molded piece.

It is evident that the only proper. way of re' moving a piece orseparating it from the part of the mold to which it is held by ridges orscrew threads, whether these be on the core or in the cavity, is byrotating either one or the other member of the mold while the piece isheld from rotation by the corresponding member of the mold. While I haveshown means for rotating the lower part or die cavity of the mold, itwould be apparent to thoseversed in the art that-the reverse could beaccomplished just as easily along the same principles, resulting inexactly the same effect. The rotating mold member however, must remainstationary at certain periods in the mold cycle, while on the otherhand, it should start to rotate at a definite point in the cyclecorresponding with the positionof the ram so that, the properrelationship would exist, permitting the molded piece to undo itselffrom the one or thel unscrewingof the piece from the threaded mold moldand the lower crosshead 44 has been `de j My device is of ,suchconstruction and mode-of operatlonthat it will act in synchrcnism withany automatic molding pressif'properly mounted.

It consists of a new and vngrvel die holder: l2, resting on the lowerplaten-Ill.4 and provided with a spindle or extension I,..cbnne cted tothe shaft 40 of motor il bymeans tcfa couplins Il. Buitablebearings forrotating the die holder 32 111W part while the piece is still held fromrotating with respect to the other mold part. Variable speed devices ormotors may be resorted to, although not essential, in presenting theprinciples of my invention. For general purposes, I have found thegeared head motor with the connection 39 made to the slow speed shaftquite satisfactory, operatingthe slow speed at a rate approximately suchas to work in harmony with the travel of ram II and the axial distancecovered in unscrewing the molded piece completely from the threaded moldmember just before it is freed fromthe corresponding retaining moldmember. To operate my device successfully, however, requires sensitiveand positive switching devices so that the motor will start at theproper moment in the molding cycle as well as stop from rotating at thelproper time. It is evident that therotation must not start before thepressure between the mold members is released and must not continueafter the prsure has commenced to be applied.

The switching arrangement comprises the .l

quired where the motor must remain stationary.

I haveprovided a lever 51,mountedvwithin the Fig, 6.' This constructionprovides interlocking housing 63 and urged by the spring- 52 against 3the switch button I. Assuming that normally when the mold is openrotation is to take place, then a normally open switch might be used sothat in the position shown, Fig. `1, the circuit would be closed and themotor rotating the mold member, While the switch in Fig. 3 would be openand the rotation stopped. In order to stop the motor at the desiredperiod in the cycle, a switch finger is attached to side rod 53 of frameI2 and placed at such a point or distance from lever 51 that it willbreak the circuit at the desired time and hold it open until returned tothat same posi.- tion. From previous descriptions it is underengagementbetween the die 3| and the molded f article to hold the article-againstrotation in the die cavity but permitting stripping of the article fromthe cavity by opening of the mold. If, on the other hand, the reversecondition exists and threadsor ridges are formed on the outside of themolded piece, provision would naturally be made on the punch 28 to holdthe molded stood that frame I2 is actuated or moved by the lost motionbetween the lever 51 and the. contact y point 6I of the switch can benoted and, as described above, varied to suit the need of the particularmold and molded piece being made.

In molding an article from plastic molding material including in itsinner or outer surfaces ridges, undercutsscrew threads and -so forth,the cycle of operation of my machine might be as follows: With the moldopen as shown in Figs. 1 and 2, and ram II starting on its down stroketo close the mold, a charge of material already measured out will bedelivered to the cavity 30 by the measuring and feeding device I1. Assoon as the molding compound is delivered into the mold cavity itcommences to heat up' from the temperature at which the die 3| is keptand as the punch 28 also at the desired temperature enters the moldcavity 30, it compresses the molding compound within the cavity against`the springs 42, reducing the powder to a plastic state, graduallyforcing some of this plastic mass out Voverthe brim of the cavity untilthe mold is completely closed. The controller and 'timer 23 hold themold closed for the predetermined time during which time the moldingcompound is -formed into the proper shape and cured suiiiciently so thatit will retain its shape and resist distortion when ejected. lAt thispoint in the cycle the motor I8 is started through the action ofcontroller 20 and retracts ram I I and with the ram frame I2 and punch2B.

On guide rod 53, (Fig. 3) of frame I2 is clamped the trip finger 54extending out from collar 55 and touching at 55 the switch lever 51 whenthe mold is closed.A As shown in Fig. 3V lever 51 is depressed away fromswitch button 5I and therefore the current supply of power to motor I6is broken and the die hoiderstationary. As the frame I2 retractstogether with the ram and punch, it permits spring 52 to cause lever-51to contact the switch button 5I', establishing a cu-rrent supply tomotor I8 which immediately will start to rotate the die holder 32. andthe combined action of the retracting ram andthe rotating die unscrewsthe molded piece.l To keep the molded piece rotating with the die 3| soas to unscrew itself like a, nut from the threaded punch, ridges orflutes, and ribs are provided as indicated at a Fig. 3,l or as indicatedat. inA

piece from rotating in relation to itwhile the ram was retracting andthe unscrewing 'process proceeded. It will bel understood that as themolded piece is being unscrewed from the punch. the force produced byco-action of the threads on the punch and on the molded piece is sum--cient to strip the raised ring 29 from the gasket recess 41. The moldingmaterial is sufiiciently elastic at the time of stripping to permitstripping of the ring 29 from the recess 41 withoutshea'ring or breakingthe wall of the recess. The threaded part of punch 28 may be taperedsomewhat so that the outer threads on the molded cap will not offer anysubstantial resistance to stripping of the ring 2B from the cap, seeFigure 7. If desired, the threadson the punch may be formed with adiameter4 slightly larger than the diameter of ring 29. Through theaction.of the-` l controller, the unscrewed molded piece is blown oi thesurface of the die 3i as soon as freed Inuenced by the movement of ram II and frame from punch 28. The air jets 64 being operated at the propertime fbycontroller 20. directing the discharging of the molded pieceinto operation check I9, thus insure continuity of operation. The moldedpiece having been delivered to the operation check I9, theram willcommence to close the mold again causing a measured charge of materialto be delivered into the cavity 30.

l2, the switch l5 is openedI at the proper point and the rotation of thedie stopped.

The cavity in die 3i is preferably tapered as shown in Figure wherebyfrictional or adhesive contact between the molded article and the diecavity is broken by the initial opening movement v of the mold,v but thedie still maintains interlocking engagement with the moldedfarticle andprevents the article from rotating with respect thereto until thearticle has been completely unscrewed from the threaded mold part. Thetapered shape of the die cavity not only permits the breaking ofadhesive contact between the molded article and the die cavity, but italso provides a, certain clearance space between the molded article andthe die cavity whereby air under pressure from the jets 6I may enter thef die cavity and assist in ejecting the article from the cavity and intothe operation check I9. It

will also be noted that the die 3| is being rotated at the time the airjets are directing an air blast vagainst the article. and the spinningof the article'while being acted on by the air blast prevents anytendency of the molded article to cock and stick in the cavity.

It will be obvious to thoseskilled in the art to which the inventionrelates that modifications.

may be madein details of construction and improvement without departingfrom the spirit of the invention which is not limited in respect to suchmattersv or otherwise than as the prior art,

and the appended claims may require. y

I claim: i

1. In a machine for molding articles from plastic material, thecombination of a mold comprising a lower mold part having a moldingcavity formed therein and an` upper mold part, one of said mold partsbeing movable to'open and close the mold, means for mounting one ofvsaid mold parts for rotation about a verticalaxis, one of said moldparts having a threaded portion for forming screw threads on-a moldedarticle, and the opposite mold part having a molding portion moldedarticle to prevent rotation of the molded article with respect theretobut permitting stripyping of the molded article therefrom by the openingof the mold, means for separating said mold parts to break the adhesive'contact between said article and said opposite mold part whilemaintaining interlocking engagement therebetween, and means responsiveto the initial opening movement of saidmold for rotating said rotatablemold part in timed relation with the separation of said mold parts to becompletely unscrew the molded article from the threaded mold part while,

said article is in interlocking engagement with said opposite mold part.

2. In a machine for molding articles from plastic material. thecombination of amold c'omprising a lower mold part having a moldingcavity formed therein and an upper mold part, one o! said mold partsbeing movableto open and close the mold. means lfor mounting one of saidmold parts for rotation about a vertical asis, o ne of said mold partshaving a threaded portipn for forming screwthreads on a molded article.and the opposite mold part having a molding portion providing aninterlocking engagement with the molded article to prevent rotation ofthe molded article with respect thereto but permitting stripping of, themolded article therefrom by the opening of the mold, means forseparatlng said mold parts to break the adhesive contact between saidarticle and said opposite mold part while maintaining interlockingengagement therebetween, means for rotating said rotatable mold part intimed relation with the separation of said mold parts to completelyunscrew the molded article from the threaded mold part while -saidarticle is in interlocking engagement with said opposite mold part, andmeans controlled in' time relation with the opening of said mold fordirecting an air blast against said article to eject said article fromsaid cavity when said article becomes unscrewed from said threaded moldpart, saidcavity being tapered to permit air from said blast to enterthe cavity 'beneath said article.

s. In s machine for molding articles from plastic material, the,combination -of a two-part mold comprising .a lower mold lpart having amolding cavity formed therein andan upper mold part having a threadedportionfor forming screw threads on -a molded article, one of vsaid moldparts being movable to open and closeithe mold. means for mounting oneof said mold parts for relative rotation with respect to the other moldpart, said lower mold part havinga molding por' -tion providing aninterlocking engagement `with t the molded article to prevent rotationofthe molded article with respect thereto but permitung stripping f themolded article therefrom byf the opening of the mold. means forseparating said mold parts to break the adhesivo contact betweensaidarticle and said lower 'mold part while' maintaining interlockingengagement therebetween, means for rotating said rotatable a :I l. c A 1j I mamans providing an interlocking engagement with the mold part 1ntimed relationship with the sepaf ration of said mold parts tocompletely unscrew the molded article from the threaded mold part whilesaid article is in interlocking engagement 5 with said lower mold part,and means controlled in timedv relation with. the opening of said moldfor directing an air blast against said article to eject said articlefrom said cavity when said article becomes unscrewed from said threadedmold part, said cavity being tapered to permit air from said blast toenter the cavity beneath said article.

4. A machine according to claim 3 wherein the lower mold part containingthe molding cavity is the rotatable mold part, and said air blast is di--rected against said article while said article is being rotated by saidrotatable mold part.

5. Ina machine for moldingarticles from plastic material, thecombination `of a-mold comprising a lower mold part having a moldingcavity formed therein and an upper mold part. one of said mold partsbeing movable to open and close the mold, means for mounting one of saidmold parts for rotation about a vertical axis, one of said mold partshaving a threaded portion for L forming screw threads on the moldedarticle, and the opposite mold part having a molding portion providingan interlocking engagement with the molded article tovprevent rotationof thesaid rotating means to break adhesive contact,

'betweensaid article and the interlocking mold part by separation ofsaid mold parts and to break adhesive contact between the molded articleand the threaded mold part by operating said rotating means duringseparation of said mold parts 5 and prior to removal .of said articlefrom interlocking engagement with said interlocking mold part.

In a method of forming hollow articles wherein the articles are moldedbetween two separable molding parts, one of said partshaving a moldcavity and theother having a core part entering said cavity, and whereinone of said mold parts is provided with a threaded portion for formingscrew threads on the molded article and the opposite moldf part has amolding portion providing an interlocking engagement with-the moldedarticle to prevent rotation of the molded article with respect theretobut permitting stripping of the molded article therefrom by separasotion of said mold parts, the steps of: breaking adhesive contact betweenthe molded article and the interlocking mold part by separating saidmold parts, and breaking adhesive contact be'- tween said article andthe threaded mold part by o5 rotating-one of said mold parts in adirection to unscrew the'molded article from the threaded mold partduring separation of said mold parts and prior to removal of saidarticle from inter- "locking engagement with said interlocking moldpart:

. y" WILLIAM STRAUSS.

